In a multi-substrate reaction, the Ping-Pong mechanism is characterized by:
The release of one product before the second substrate binds correctly identifies the characteristic feature or property described in this question. In Enzyme Kinetics, specific characteristics define and distinguish biological molecules, organisms, or processes from one another. The feature described by The release of one product before the second substrate binds is a defining property that arises from its unique molecular structure, evolutionary history, or physiological role. The other options (The simultaneous binding of two substrates, The formation of a ternary enzyme complex, and The requirement of a metal cofactor) describe characteristics of different entities, represent incorrect properties, or apply to the subject under different conditions.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 6